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https://github.com/esphome/esphome.git
synced 2026-02-08 00:31:58 +00:00
[dsmr] Batch UART reads to reduce per-loop overhead
Replace byte-at-a-time read() calls with batched read_array() in all four UART read sites: receive_telegram_(), receive_encrypted_telegram_(), and two drain loops. Each read() internally chains through read_array(data, 1) -> check_read_timeout_(1) -> available(), resulting in ~3 UART driver calls per byte. Batching into a 64-byte stack buffer reduces this to ~3 calls per batch regardless of byte count. Extract drain_rx_buffer_() helper to deduplicate the two drain sites in ready_to_request_data_() and stop_requesting_data_().
This commit is contained in:
J. Nick Koston
@@ -40,9 +40,7 @@ bool Dsmr::ready_to_request_data_() {
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this->start_requesting_data_();
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}
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if (!this->requesting_data_) {
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while (this->available()) {
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this->read();
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}
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this->drain_rx_buffer_();
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}
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}
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return this->requesting_data_;
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@@ -115,13 +113,19 @@ void Dsmr::stop_requesting_data_() {
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} else {
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ESP_LOGV(TAG, "Stop reading data from P1 port");
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}
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while (this->available()) {
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this->read();
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}
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this->drain_rx_buffer_();
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this->requesting_data_ = false;
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}
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}
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void Dsmr::drain_rx_buffer_() {
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uint8_t buf[64];
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int avail;
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while ((avail = this->available()) > 0) {
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this->read_array(buf, std::min(static_cast<size_t>(avail), sizeof(buf)));
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}
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}
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void Dsmr::reset_telegram_() {
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this->header_found_ = false;
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this->footer_found_ = false;
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@@ -133,120 +137,144 @@ void Dsmr::reset_telegram_() {
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void Dsmr::receive_telegram_() {
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while (this->available_within_timeout_()) {
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const char c = this->read();
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// Read all available bytes in batches to reduce UART call overhead.
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uint8_t buf[64];
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int avail = this->available();
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while (avail > 0) {
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size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
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if (!this->read_array(buf, to_read))
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return;
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avail -= to_read;
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// Find a new telegram header, i.e. forward slash.
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if (c == '/') {
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ESP_LOGV(TAG, "Header of telegram found");
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this->reset_telegram_();
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this->header_found_ = true;
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}
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if (!this->header_found_)
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continue;
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for (size_t i = 0; i < to_read; i++) {
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const char c = static_cast<char>(buf[i]);
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// Check for buffer overflow.
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if (this->bytes_read_ >= this->max_telegram_len_) {
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this->reset_telegram_();
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ESP_LOGE(TAG, "Error: telegram larger than buffer (%d bytes)", this->max_telegram_len_);
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return;
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}
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// Find a new telegram header, i.e. forward slash.
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if (c == '/') {
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ESP_LOGV(TAG, "Header of telegram found");
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this->reset_telegram_();
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this->header_found_ = true;
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}
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if (!this->header_found_)
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continue;
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// Some v2.2 or v3 meters will send a new value which starts with '('
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// in a new line, while the value belongs to the previous ObisId. For
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// proper parsing, remove these new line characters.
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if (c == '(') {
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while (true) {
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auto previous_char = this->telegram_[this->bytes_read_ - 1];
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if (previous_char == '\n' || previous_char == '\r') {
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this->bytes_read_--;
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} else {
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break;
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// Check for buffer overflow.
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if (this->bytes_read_ >= this->max_telegram_len_) {
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this->reset_telegram_();
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ESP_LOGE(TAG, "Error: telegram larger than buffer (%d bytes)", this->max_telegram_len_);
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return;
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}
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// Some v2.2 or v3 meters will send a new value which starts with '('
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// in a new line, while the value belongs to the previous ObisId. For
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// proper parsing, remove these new line characters.
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if (c == '(') {
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while (true) {
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auto previous_char = this->telegram_[this->bytes_read_ - 1];
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if (previous_char == '\n' || previous_char == '\r') {
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this->bytes_read_--;
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} else {
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break;
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}
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}
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}
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// Store the byte in the buffer.
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this->telegram_[this->bytes_read_] = c;
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this->bytes_read_++;
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// Check for a footer, i.e. exclamation mark, followed by a hex checksum.
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if (c == '!') {
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ESP_LOGV(TAG, "Footer of telegram found");
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this->footer_found_ = true;
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continue;
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}
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// Check for the end of the hex checksum, i.e. a newline.
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if (this->footer_found_ && c == '\n') {
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// Parse the telegram and publish sensor values.
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this->parse_telegram();
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this->reset_telegram_();
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return;
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}
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}
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}
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// Store the byte in the buffer.
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this->telegram_[this->bytes_read_] = c;
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this->bytes_read_++;
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// Check for a footer, i.e. exclamation mark, followed by a hex checksum.
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if (c == '!') {
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ESP_LOGV(TAG, "Footer of telegram found");
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this->footer_found_ = true;
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continue;
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}
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// Check for the end of the hex checksum, i.e. a newline.
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if (this->footer_found_ && c == '\n') {
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// Parse the telegram and publish sensor values.
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this->parse_telegram();
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this->reset_telegram_();
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return;
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}
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}
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}
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void Dsmr::receive_encrypted_telegram_() {
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while (this->available_within_timeout_()) {
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const char c = this->read();
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// Read all available bytes in batches to reduce UART call overhead.
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uint8_t buf[64];
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int avail = this->available();
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while (avail > 0) {
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size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
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if (!this->read_array(buf, to_read))
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return;
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avail -= to_read;
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// Find a new telegram start byte.
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if (!this->header_found_) {
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if ((uint8_t) c != 0xDB) {
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continue;
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for (size_t i = 0; i < to_read; i++) {
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const char c = static_cast<char>(buf[i]);
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// Find a new telegram start byte.
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if (!this->header_found_) {
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if ((uint8_t) c != 0xDB) {
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continue;
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}
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ESP_LOGV(TAG, "Start byte 0xDB of encrypted telegram found");
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this->reset_telegram_();
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this->header_found_ = true;
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}
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// Check for buffer overflow.
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if (this->crypt_bytes_read_ >= this->max_telegram_len_) {
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this->reset_telegram_();
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ESP_LOGE(TAG, "Error: encrypted telegram larger than buffer (%d bytes)", this->max_telegram_len_);
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return;
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}
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// Store the byte in the buffer.
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this->crypt_telegram_[this->crypt_bytes_read_] = c;
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this->crypt_bytes_read_++;
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// Read the length of the incoming encrypted telegram.
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if (this->crypt_telegram_len_ == 0 && this->crypt_bytes_read_ > 20) {
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// Complete header + data bytes
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this->crypt_telegram_len_ = 13 + (this->crypt_telegram_[11] << 8 | this->crypt_telegram_[12]);
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ESP_LOGV(TAG, "Encrypted telegram length: %d bytes", this->crypt_telegram_len_);
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}
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// Check for the end of the encrypted telegram.
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if (this->crypt_telegram_len_ == 0 || this->crypt_bytes_read_ != this->crypt_telegram_len_) {
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continue;
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}
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ESP_LOGV(TAG, "End of encrypted telegram found");
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// Decrypt the encrypted telegram.
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GCM<AES128> *gcmaes128{new GCM<AES128>()};
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gcmaes128->setKey(this->decryption_key_.data(), gcmaes128->keySize());
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// the iv is 8 bytes of the system title + 4 bytes frame counter
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// system title is at byte 2 and frame counter at byte 15
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for (int i = 10; i < 14; i++)
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this->crypt_telegram_[i] = this->crypt_telegram_[i + 4];
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constexpr uint16_t iv_size{12};
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gcmaes128->setIV(&this->crypt_telegram_[2], iv_size);
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gcmaes128->decrypt(reinterpret_cast<uint8_t *>(this->telegram_),
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// the ciphertext start at byte 18
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&this->crypt_telegram_[18],
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// cipher size
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this->crypt_bytes_read_ - 17);
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delete gcmaes128; // NOLINT(cppcoreguidelines-owning-memory)
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this->bytes_read_ = strnlen(this->telegram_, this->max_telegram_len_);
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ESP_LOGV(TAG, "Decrypted telegram size: %d bytes", this->bytes_read_);
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ESP_LOGVV(TAG, "Decrypted telegram: %s", this->telegram_);
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// Parse the decrypted telegram and publish sensor values.
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this->parse_telegram();
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this->reset_telegram_();
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return;
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}
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ESP_LOGV(TAG, "Start byte 0xDB of encrypted telegram found");
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this->reset_telegram_();
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this->header_found_ = true;
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}
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// Check for buffer overflow.
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if (this->crypt_bytes_read_ >= this->max_telegram_len_) {
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this->reset_telegram_();
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ESP_LOGE(TAG, "Error: encrypted telegram larger than buffer (%d bytes)", this->max_telegram_len_);
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return;
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}
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// Store the byte in the buffer.
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this->crypt_telegram_[this->crypt_bytes_read_] = c;
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this->crypt_bytes_read_++;
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// Read the length of the incoming encrypted telegram.
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if (this->crypt_telegram_len_ == 0 && this->crypt_bytes_read_ > 20) {
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// Complete header + data bytes
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this->crypt_telegram_len_ = 13 + (this->crypt_telegram_[11] << 8 | this->crypt_telegram_[12]);
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ESP_LOGV(TAG, "Encrypted telegram length: %d bytes", this->crypt_telegram_len_);
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}
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// Check for the end of the encrypted telegram.
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if (this->crypt_telegram_len_ == 0 || this->crypt_bytes_read_ != this->crypt_telegram_len_) {
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continue;
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}
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ESP_LOGV(TAG, "End of encrypted telegram found");
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// Decrypt the encrypted telegram.
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GCM<AES128> *gcmaes128{new GCM<AES128>()};
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gcmaes128->setKey(this->decryption_key_.data(), gcmaes128->keySize());
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// the iv is 8 bytes of the system title + 4 bytes frame counter
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// system title is at byte 2 and frame counter at byte 15
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for (int i = 10; i < 14; i++)
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this->crypt_telegram_[i] = this->crypt_telegram_[i + 4];
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constexpr uint16_t iv_size{12};
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gcmaes128->setIV(&this->crypt_telegram_[2], iv_size);
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gcmaes128->decrypt(reinterpret_cast<uint8_t *>(this->telegram_),
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// the ciphertext start at byte 18
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&this->crypt_telegram_[18],
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// cipher size
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this->crypt_bytes_read_ - 17);
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delete gcmaes128; // NOLINT(cppcoreguidelines-owning-memory)
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this->bytes_read_ = strnlen(this->telegram_, this->max_telegram_len_);
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ESP_LOGV(TAG, "Decrypted telegram size: %d bytes", this->bytes_read_);
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ESP_LOGVV(TAG, "Decrypted telegram: %s", this->telegram_);
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// Parse the decrypted telegram and publish sensor values.
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this->parse_telegram();
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this->reset_telegram_();
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return;
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}
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}
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@@ -85,6 +85,7 @@ class Dsmr : public Component, public uart::UARTDevice {
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void receive_telegram_();
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void receive_encrypted_telegram_();
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void reset_telegram_();
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void drain_rx_buffer_();
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/// Wait for UART data to become available within the read timeout.
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///
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